While fuel-air combustion chambers and catalytic reaction devices have been used together before, as shown in U.S. Pat. Nos. 3,797,231 and 3,846,979, the arrangement described herein is believed to define thereover.
There are two primary classes of objectionable gaseous exhaust emissions that are of concern with relation to gas turbine engine burner operation. The first is the low temperature class in which carbon monoxide (CO) and unburned hydrocarbons (UHC) are components. These species persist in exhaust gas from burners because the temperature within the burner was too low for the combustion reaction to be completed in which the CO and UHC would have been completely oxidized to carbon dioxide (CO.sub.2) and water (H.sub.2 O). The second class is the high-temperature class in which the oxides of nitrogen (NO.sub.x) are components. These species persist in exhaust gas from burners because the temperature within the burner was too high and the nitrogen and oxygen in the air reacted together. In general, means incorporated to control low-temperature pollutants increase concentrations of the high-temperature species, and means incorporated to control high-temperature species increase concentrations of the low-temperature species. Both low and high-temperature species can be controlled if the temperature in the burner can be controlled. The ideal operating temperatures within which pollutant control can be accomplished is 2200.degree.-3050.degree. F. Below 2200.degree. F., carbon monoxide ceases to further oxidize to carbon dioxide. The temperature 2200.degree. F. is referred to as the kinetic "freezing point" temperature for carbon monoxide. Above 3050.degree. F., the rate of formation of the oxides of nitrogen increases rapidly with temperature; at temperatures of 3050.degree. F. and below, the rates of formation of the oxides of nitrogen are low and, consequently the concentrations of NO.sub.x in the burner exhaust gas are low.